Are you experiencing some slowness in ARCHICAD 21? Especially with MacOs High Sierra? Here's a tip to increase your performance. It's a little drastic but it works.
First of all make a backup of your work environments and any custom schemes or translators. Ensure no projects, libraries or any other data exist in your ARCHICAD 21 folder as we're about to nuke it all. Same goes for add-ons. You'll probably need to reisntall those here soon. So just to keep me out of trouble, I will advise to do a system backup first and know that this procedure may be more involved if you have multiple add-ons, haven't saved your work environment, etc or are just not too familiar with installing applications. In any case read through everything before starting:
So Step 1: Uninstall ARCHICAD 21. Windows users, use the uninstaller that comes with ARCHICAD rather than the Control Panel. It's more thorough.
Step 2: Clean your Preferences, by following the instructions at http://helpcenter.graphisoft.com/troubleshooting/setup/preferences-cleaning/
Step 3: Restart your computer. For Mac users: clear the PRAM (hold down Command+Option+P+R keys while rebooting until you hear the startup chime 3 times) just to make sure no old memories remain.
Step 4: Download ARCHICAD 21 again from http://www.graphisoft.com/downloads/ and reinstall it.
Step 5: Update ARCHICAD 21 by using the Check For Updates Command or by downloading the updater at http://www.graphisoft.com/downloads/updates/ARCHICAD_Updates.html
Step 6: Reload your work environments, schemes, translators, add-ons, etc.
Step 7: Enjoy your fast display and performance issues.